The Grenfell Tower fire in London has given rise to questions about how such a disaster could have happened, whether it could happen elsewhere, and what might be learned from it to prevent recurrences.

As a professor of fire-protection engineering, I know that the answers are not simple, and the remedies not quick.

Investigations into what actually happened at Grenfell Tower are still ongoing. While some contributing circumstances have been identified, it could take years to complete the picture. As details emerge, though, it may not be easy to understand their implications for other situations.

Buildings differ greatly from each other, varying in things such as when they were constructed and whether any renovations or other modifications have occurred since. And then there are the different rules, design ideas and construction practices that vary from country to country, and, in the U.S., sometimes from state to state.

The basic situation is clear, however: The Grenfell Tower fire spread much faster and more intensely than anyone had expected. From what we know so far, there are physical, cultural and legal reasons that dozens, and possibly hundreds, of people died.

Structure

It appears that the main flaw was in the dangerously inflammable cladding, the material covering the outside of the building. The aluminum panels with foam insulation were installed in a recent effort to improve the building’s energy efficiency. Once the fire escaped the apartment where it began, apparently in the refrigerator, and ignited the cladding, the rest of the building was primed to burn quickly.

Additional insulation underneath that cladding may have released poisonous fumes as it burned, overcoming residents who might otherwise have escaped the flames.

In addition, the building lacked an automatic fire-sprinkler system, and had only a single stairway offering a way out.

Culture

That lone stairway – and the fact that building occupants were apparently told to remain in their apartments in case of fire – are the result of fire safety culture influencing emergency planning. In England and other places in the world, including the U.S., the historical approach has been to rely significantly on the fire resistance of the structure itself to contain the fire. We call this “passive” fire protection, and it largely involves using non-combustible materials to separate areas, limiting how far a fire can spread.

This system has been used at least since the 1666 Great Fire of London, as a way to prevent city-wide conflagrations from developing after a blaze burning in one building catches the structure next door on fire. The same principle is used within buildings, by, for example, requiring fire-resistant features between apartments or offices on each floor, as well as between floors.

However, the system works only when the initial fire is contained. That didn’t happen at Grenfell Tower. Once the fire reached the building’s external cladding, it spread rapidly. If the residents had their windows open for ventilation, the fire could have spread even faster: The heat just outside could have ignited drapes or other things near the windows.

With more than one fire burning simultaneously in different apartments on several floors, the situation would have been grim. The building had no sprinklers to quench the flames. And the only stairway occupants could have taken to get out was the same one firefighters had to take up.

Rules

Those expectations about how structures will hold up in a fire inform the rules people make about how to protect occupants of a burning building. In most countries, including the U.S., the rules governing how buildings are constructed are enforced when a new structure is going up.

As we learn more over time about how to keep people safer, building codes change – but they usually apply just to new structures, not existing ones. The new codes can kick in if there’s a big renovation or expansion project or the building’s main use changes from, say, offices to apartments. That means many buildings aren’t up to modern standards.

In addition, it takes time from when a model building code is published, to when it becomes adopted into legislation. As such, even a building put up in 1997, if it hadn’t been significantly renovated, may not have to comply with new provisions introduced in the 20 years since.

There are some exceptions. Many parts of the U.S. required building owners to install automatic sprinkler systems in existing high-rise buildings in the wake of the 1980 MGM Grand Hotel fire in Las Vegas. A similar requirement in the U.K. didn’t take effect until 2007; existing buildings are not covered unless a specific risk assessment recommends otherwise.

Could it happen here?

There have been many exterior-cladding fires in high-rise buildings around the world, including in Australia, the Middle East and here in the U.S. In September 2007, the Water Club tower at the Borgata Casino hotel in Atlantic City, New Jersey, caught fire. The building was under construction at the time, so it was largely unoccupied. And there was a concrete wall separating the burning cladding from the rest of the building.

In the U.S., most fire codes restrict the use of combustible exterior-cladding material, particularly on high-rise buildings. The requirements for automatic sprinklers (one part of what we call “active” fire protection systems) and at least two escape routes from every floor help bolster these defenses. Together, these rules increase the chance that a small fire will be put out quickly, reduce its ability to spread up the side of the building, and help people get out if they need to.

Several other Grenfell Tower-like buildings have already been identified in the U.K. These high-rises have combustible cladding or insulation which was either permitted at the time of construction or perhaps added during a retrofit. Some of those buildings may not have sprinklers, either. The thousands of residents of those buildings have been moved out to prevent a repeat disaster.

But at least in the U.S., most will have both sprinklers and more than one escape route. So while another disaster like the Grenfell Tower fire is possible, we can hope that building owners and fire-protection experts alike will learn from this catastrophe and work even harder to prevent something like it from happening again.

This article was originally published on The Conversation, an independent and nonprofit source of news, analysis and commentary from academic experts.